Loss of WHY1 has Specific Effects on C/N Metabolism
Several transcripts associated with primary metabolic pathways were
differentially abundant in the basal portion of wild type and WHY1
knockdown leaves (Fig. 8A). Significant differences were observed in
transcripts encoding enzymes associated with the Calvin cycle, starch
and sugar metabolism, glycolysis, the TCA cycle and amino acid
metabolism. Many of these transcripts were more abundant in WHY1
knockdown than wild type leaves although transcripts encoding hexokinase
(MLOC_54094.1), β-amylase (AK368826) a methionine S-methyltransferase
(AK368357), an O-acetylcysteine thiol-lyase (AK248898.1) and an arginase
(MLOC_65968.1) were consistently less abundant in WHY1 knockdown lines.
Differences in transcript abundance were reflected by significant
differences in primary metabolic profiles (Fig. 8B). Twenty-two of 71
polar compounds analysed by GC/MS were significantly differentially
abundant in wild type and WHY1 knockdown leaf basal regions. Eight of
these compounds were unidentified with the remainder comprising
primarily organic and amino acids. All of the TCA cycle components
detected were significantly lower in WHY1 knockdown leaves than in wild
type leaves as was the non-proteinaceous amino acid γ-amino butyric acid
(GABA) that functions as a cytosolic bypass of specific steps
(Sweetlove, Beard, Nunes-Nesi, Fernie, & Ratcliffe, 2010). Similarly,
serine and aspartate were present at lower concentrations in WHY1
knockdown leaves while glycine, valine, leucine, threonine and
isoleucine were present at higher concentrations, particularly in W1-7
(Fig. 8B).